Cryoablation - A Minimally Invasive Surgery

Introduction:

Cryoablation, also called cryotherapy, uses extreme cold to kill diseased tissues in the body.

Ablation is the removal or destruction of body parts or tissue or function. It can be performed by surgery, drugs, extreme cold, radiofrequency and other methods.Cryoablation is performed in topical, percutaneous, and surgical (open cryotherapy) ways. Topical cryoablation procedures do not need painkillers or general anesthesia, which is performed over the skin. The percutaneous procedure requires only a small cut through which a needle or tube is inserted to destroy the abnormal cells rather than an open approach.

What Are the Uses of Cryoablation?

Cryoablation is used to treat the following conditions:

• Skin tags.

• Skin moles.

• Arrhythmia (a condition that causes irregular heartbeat).

• Skin cancer.

• Retinoblastoma (eye cancer that begins in the retina).

• Prostate cancer.

• Liver cancer.

• Cervical cancer.

• Fibroadenomas (breast tumor).

• Bone cancer.

• Kidney cancer.

• Lung cancer.

How Do the Patients Prepare for the Cryoablation Procedure?

• Patients are instructed to take antibiotics before the procedure to prevent the risk of infections. Some skin problems require Ibuprofen before the procedure, which helps to relieve the pain and discomfort in the patients.

• The patient's allergic reactions to contrast materials and local or general anesthesia should be informed to the health provider.

• Medical conditions and regular medicines of the patients should be informed to the doctor.

• Patients might not be advised to drive or operate machinery for about 24 hours after some cryoablation procedure. They have to arrange for someone to bring them home.

• Patients taking antiplatelet or blood-thinning medicines are instructed to stop it a few days before the procedure with their physician's permission.

• The patient should inform if she is a pregnant woman.

How Does Cryoablation Work?

Cryoablation works by means of the following principles:

1. Thermodynamics: When the cryoprobe is placed into the target site, it is cooled rapidly and removes heat from the tissues surrounding the cryoprobe. This rapid cooling is caused by the Joule-Thomson effect or the Joule-kelvin effect. Under room temperature and pressure, there is a temperature change accompanied by gas expansion without producing work called the Joule-Thompson effect. Except for helium and hydrogen, gasses such as oxygen, argon, and nitrogen exhibit this effect. Helium and nitrogen are warmed when they rapidly expand at room temperature. Argon gas is typically released in cryoablation through the cryoprobe, which undergoes rapid expansion and cooling.

2. Direct and Indirect Cellular Injury:

• Direct Cellular Injury: When the cryoprobe absorbs heat from the surrounding tissue and releases extreme cold, it results in the formation of ice crystals at the tip of the probe. The cooling rate is more near the cryoprobe and less outside the area of the ice ball. Intracellular (inside the cell) water comes outside the cells by osmotic tension and is dehydrated. This causes damage to the cellular enzymes and the destruction of the cell membrane. This results in apoptosis or programmed cell death. When the abnormal cells are rapidly cooled below - 40 degrees celsius, they result in cell death.

• Indirect Cellular Injury: Cryoablation releases extreme cold, which causes cells of the blood vessels to be damaged. This results in cellular ischemia. Once the cells are destroyed, inflammatory cells such as neutrophils and macrophages surround the area of coagulation necrosis, which helps clear the dead cells. This process will happen for about weeks to months after the cryoablation.

How Is the Cryoablation Procedure Performed?

• For topical cryoablation, liquid nitrogen is directly placed over the target site as a spray or cotton swab.

• During the percutaneous procedure, patients are instructed to lie flat on their stomachs or on their sides over the procedure table.

• Patients may be given an intravenous line (IV) to administer a sedative to relax them. Local anesthesia is given to numb the area where the needle will be inserted. Then, a hollow needle-like wand called a cryoprobe is inserted into the target area guided by fluoroscopy (X-ray video). Sometimes, multiple cryoprobes are required to destroy the abnormal tissues (like in prostate cancer).

• Once the cryoprobe is inserted into the intended site, they deliver liquid nitrogen, liquid nitrous oxide, or compressed argon gas.

• Healthtronic cryoablation system and Galil medical’s cryoablation system are the two commercially available cryoablation systems in the United States.

• Doctors touch the diseased tissues with the cryoprobe under imaging guidance. This device decreases the temperature at the tip of the cryoprobe, resulting in the formation of ice crystals. This ice crystal is visible in imaging techniques. This freezes the abnormal cells around the tip of the cryoprobe. This entire process is monitored via imaging.

• Once the procedure is finished, doctors remove the cryoprobe and close the area with the dressing. Usually, sutures are not required for this procedure.

• This procedure usually takes about one to three hours to complete.

• After open cryosurgery, patients are instructed to continue their regular activities after a week.

What Is the Role of Cryoablation in Cardiac Arrhythmia?

1. Cryoablation freezes the abnormal heart tissues or blocks the abnormal pathways, which alters the normal electrical pulses.

2. Cryoablation is also used to detect the abnormal heart tissues which cause arrhythmia. They detect abnormal tissues by temporarily blocking the electric pulses of the heart by rapid cooling. This procedure is called site testing or cryo mapping.

3. For arrhythmia, cryoablation is done in two ways:

• Catheter-Based: A thin, flexible tube called a catheter is placed into the target area and delivers extreme cold to block the abnormal electrical pulses.

• Surgical: Cryosurgery may be recommended during open-heart surgery as a secondary treatment option for arrhythmia.

What Are the Complications Associated With Cryoablation?

The risks of cryoablation are very less. They are:

• Cryoshock (extreme cold results in multiple organ failure) is found to be typical in large-volume liver cryoablation.

• The cryoablation equipment consists of multiple units and uses rare gas like argon.

• The frozen tissues are brittle, resulting in cryoprobe displacement, and organ fracture results in severe bleeding.

• There might be a chance of irreversible heart block by cryoablation near the AV (atrioventricular) node during the treatment of arrhythmia.

Conclusion:

Cryoablation is the primary treatment for prostate cancer patients who are not eligible for retropubic prostatectomy (surgical prostate removal). It is less expensive when compared to open surgical methods. The risks are very minimal in cryoablation than in radiofrequency ablation. As cryoablation uses the cooling effect to destroy abnormal cells, it is less painful. The cryoablation device does not interfere with CT (computed tomography) or MRI (magnetic resonance imaging) machines.